Fig 1.
A) Distribution of the main ferruginous outcrop savanna ecosystems (locally known as canga) in Brazil. In Minas Gerais State (MG), canga vegetation occurs in Serra da Canastra (1), the Iron Quadrangle (2), and Serra do Cipó (3). In Bahia State (BA), the vegetation occurs in Chapada Diamantina (4). In Pará State (PA), the vegetation occurs in Serra dos Carajás (5), Maraconaí (6), and Maicuru (7). In Amazonas State (AM), the vegetation occurs in Serra dos Seis Lagos [24], while in Mato Grosso do Sul (MS), the vegetation occurs in Morraria de Urucum (9). N1, N4, N5, N8, S2, S11, S23, S38, and S43 are examples of geomorphic units located in the study area. B) The Shuttle Radar Topography Mission (SRTM) elevation map of the study area with canga vegetation before mining implementation. The red and black lines represent the boundaries of the Carajás National Forest (CNF) and the Campos Ferruginosos National Park (CFNP) protected areas, respectively. The digital elevation model (SRTM, 1 arc-second) was obtained from USGS Earth Explorer (https://earthexplorer.usgs.gov) and the CNF and CFNP shapefiles from ICMBIO (http://mapas.icmbio.gov.br/i3geo/datadownload.htm). All other layers and photos were produced by the authors and are copyright-free.
Fig 2.
Description of the land-cover and land-use classification system used in this study.
The Landsat images were obtained from USGS Earth Explorer (https://earthexplorer.usgs.gov). All photographs were taken by the authors and are copyright-free.
Fig 3.
Example of segmentation and classification carried out from the 1984 Landsat-5 TM 5R4G3B and 2016 Landsat-8 OLI 6R5G4B images.
Observed Landsat images are shown in colour composition; level 1 objects are overlaid on Landsat imagery; thematic classification for level 1 objects; level 2 objects are overlaid on imagery; and final result of thematic aggregation for level 2 objects. The Landsat images were obtained from USGS Earth Explorer (https://earthexplorer.usgs.gov). All other layers were produced by the authors and are copyright-free.
Fig 4.
Landsat images, land cover (canga, forests and lakes) and land use (N4-N5, S11D and SL mines and pasturelands) maps from 1973, 1984, 2001 and 2016 in the Carajás Mineral Province.
See location of the mines in Fig 1. The digital elevation model (SRTM, 1 arc-second) and Landsat images were obtained from USGS Earth Explorer (https://earthexplorer.usgs.gov). All other layers were produced by the authors and are copyright-free.
Fig 5.
Digital elevation model extracted from the Shuttle Radar Topography Mission (SRTM) showing canga areas (yellow polygons) (A) before implementation of mining projects and (B) currently, with mining areas (blue polygons). The limits of the two protected areas are shown, the Carajás National Forest (red line) and the Campos Ferruginosos National Park (black line), created in 1998 and 2017, respectively. The São Felix Ridge is illustrated as a window, 160 km from the South Ridge. (C) The canga areas converted to mining structures between the 1970s and 2016 over the North, South and East Ridges, and over total canga area. Letters N, S and SL represent the geographic locations of North, South, and East ridges, respectively. Other mines: a = Igarapé Bahia, b = Azul, and c = Project 118. The digital elevation model (SRTM, 1 arc-second) was obtained from USGS Earth Explorer (https://earthexplorer.usgs.gov) and the National Forest and National Park shapefiles from ICMBIO (http://mapas.icmbio.gov.br/i3geo/datadownload.htm). All other layers were produced by the authors and are copyright-free.
Table 1.
Canga areas before the implementation of mining projects (1973) and currently (2016) in different geographical sites.
See location of sites in Fig 1.
Fig 6.
LCLU change detection maps between 1973–1984, 1984–2016, and 1973–2016 for the N4-N5, S11D and SL mines.
The digital elevation model (SRTM, 1 arc-second) was obtained from USGS Earth Explorer (https://earthexplorer.usgs.gov) and the National Forest and National Park shapefiles from ICMBIO (http://mapas.icmbio.gov.br/i3geo/datadownload.htm). All other layers were produced by the authors and are copyright-free.
Table 2.
Quantification of land cover and land use changes between 1973–1984, 1984–2016, and 1973–2016 using the “from-to” object detection approach.